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FILE - In this March 30, 2009 file photo, US President Barack Obama meets with then U.S. Envoy for Sudan Major General J. Scott Gration in the Roosevelt Room of the White House in Washington. The U.S. ambassador to Kenya Scott Gration said Friday, June 29, 2012 that he is leaving his post over differences with Washington on his leadership style, adding that he resigned Monday, June 25, 2012, effective Saturday, July 28, 2012. (AP Photo/Evan Vucci, File)

FILE - In this March 30, 2009 file photo, US President Barack Obama meets with then U.S. Envoy for Sudan Major General J. Scott Gration in the Roosevelt Room of the White House in Washington. The U.S. ambassador to Kenya Scott Gration said Friday, June 29, 2012 that he is leaving his post over differences with Washington on his leadership style, adding that he resigned Monday, June 25, 2012, effective Saturday, July 28, 2012. (AP Photo/Evan Vucci, File)